A Newly Constructed Cobalt‐Organic Coordination Polymer and Its Two Carbon‐Based Composites Demonstrating Electrochemical Sensing to NO₂⁻ and Cr (VI)

A novel cobalt‐organic ionic coordination polymer, incorporating the multifunctional 2‐iodo‐4‐sulfonatobenzoate anion (isba 2 − ) and the rigid nitrogen‐containing ligand 4,4′‐bipyridine (bipy) {[Co (bipy)(H 2 O) 3 (CH 3 CH 2 OH)]·isba·2H 2 O} n (Co‐bipy), was synthesized via a straightforward solution evaporation method at room temperature. Two innovative carbon‐based composite materials Co‐bipy@MWCNTs and Co‐bipy@GO were successfully fabricated through hybridization with multi‐walled carbon nanotubes and graphene oxide, respectively. Experimental investigation indicates that the electrocatalytic ability of Co‐bipy towards the NO 2 − oxidation and Cr (VI) reduction can be enhanced by MWCNTs and GO. Among the three glassy carbon electrodes (GCE) modified with Co‐bipy, Co‐bipy@MWCNTs, and Co‐bipy@GO, the Co‐bipy@MWCNTs/GCE exhibits optimal performance for NO 2 − oxidation sensing in 0.1 M PBS and Cr (VI) reduction sensing in 0.1 M H 2 SO 4 . The successful modification of Co‐bipy@MWCNTs on the screen‐printed electrode (SPE) further enhanced the electrocatalytic performance of Co‐bipy@MWCNTs. The Co‐bipy@MWCNTs/SPE shows the most efficient sensing to NO 2 − and Cr (VI). The limits of detection (LOD) reach 0.13 μM for NO 2 − and 0.25 μM for Cr (VI), respectively. Furthermore, the Co‐bipy@MWCNTs/SPE was effectively employed for the accurate detection of NO 2 − and Cr (VI) in the actual samples. The sensing mechanisms for NO 2 − and Cr (VI) were illustrated with the aid of Hirshfeld surface analysis and density of states (DOS) calculations.